An analysis of mutants recovered after 1000 lines of a balanced lethal strain of Drosophila melanogaster were exposed to chronic low-dose (8.7 rad/hr) gamma-irradiation was carried out. The following mutants were recovered: Got-2, 1; alpha-Gpdh, 6; cMdh, 2; Adh, 0; Dip-A, 0; Hex-C, 4; alpha-Amy, 0. These represent 7 independent mutation events. Only one of these was associated with a chromosomal aberration (deficiency). Of five which could be analyzed for CRM production, three were CRM-positive. These results suggest that the majority of mutants induced by low-dose-rate gamma-irradiation are point mutations.